U.S. patent number 5,081,542 [Application Number 07/450,118] was granted by the patent office on 1992-01-14 for liquid crystal light valve goggles for eye protection.
This patent grant is currently assigned to Hughes Aircraft Company. Invention is credited to Uzi Efron, Tsung-Yuan Hsu, Wayne Schoenmakers, Shin-Tson Wu.
United States Patent |
5,081,542 |
Efron , et al. |
January 14, 1992 |
Liquid crystal light valve goggles for eye protection
Abstract
An eye protection device 10 comprising a liquid crystal light
valve 20 for providing an image of a scene. The light valve images
the field of view under observation in a spectral range which
matches the human eye. It will automatically reject a laser threat
by simply absorbing the energy therefrom in the photoconductive
layer thereof. Thus, the invention 10 provides a broad spectrum,
zero response time, angle and polarization independent, sensitive
eye protection device having a fast recovery time, high extinction
coefficient and a high damage threshold. Hence, the invention is
expected to be of significant utility to personnel operating in
hostile environments.
Inventors: |
Efron; Uzi (Los Angeles,
CA), Wu; Shin-Tson (Northridge, CA), Hsu; Tsung-Yuan
(Westlake Village, CA), Schoenmakers; Wayne (Winnetka,
IL) |
Assignee: |
Hughes Aircraft Company (Los
Angeles, CA)
|
Family
ID: |
23786833 |
Appl.
No.: |
07/450,118 |
Filed: |
December 12, 1989 |
Current U.S.
Class: |
349/11; 349/14;
349/25; 349/161 |
Current CPC
Class: |
A61F
9/067 (20130101); A61F 9/023 (20130101); G02F
1/1354 (20130101); G02F 1/1352 (20210101) |
Current International
Class: |
A61F
9/06 (20060101); A61F 9/04 (20060101); A61F
9/02 (20060101); G02F 1/135 (20060101); G02F
1/13 (20060101); G02F 001/133 (); G09G
003/02 () |
Field of
Search: |
;350/331R,338,342 ;2/426
;340/705 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Moran, "Integrated Military Aircraft Displays and Controls," SID
Digest, Apr. 1980, pp. 32-33. .
"The Silicon Liquid-Crystal Light Valve", U. Efron et al., Journal
of Applied Physics, vol. 57 (4), Feb. 15, 1985, pp.
1356-1368..
|
Primary Examiner: Miller; Stanley D.
Assistant Examiner: Gross; Anita Pellman
Attorney, Agent or Firm: Duraiswamy; V. D. Denson-Low; W.
K.
Government Interests
This invention was made in performance of work under the Department
of the Navy Contract No. N62269-87-C-0263. The Government of the
United States of America therefore has certain rights in this
invention.
Claims
Accordingly, What is claimed is:
1. An eye protection device comprising:
a liquid crystal light valve for providing an image of a scene in a
spectral range suitable for human viewing and for preventing
harmful radiation from being transmitted for viewing, wherein said
liquid crystal light valve includes a photoconductive layer,
and
means for supporting the light valve to facilitate the viewing
thereof.
2. The invention of claim 1 wherein said photoconductive layer
comprises silicon.
3. The invention of claim 2 wherein the silicon is single
crystalline silicon.
4. The invention of claim 1 wherein the photoconductive layer
comprises lead salts.
5. The invention of claim 1 including an objective lens mounted
along the optical train of said light valve.
6. The invention of claim 5 including an eyepiece lens mounted
along the optical axis of said light valve.
7. The invention of claim 1 including light emitting diode means
for reading said light valve.
8. The invention of claim 1 including reflector means for
reflecting said image to the eye of a viewer.
9. An eye protection device comprising:
a liquid crystal light valve for providing an image of a scene;
means for supporting the light valve to facilitate the viewing
thereof;
reflector means for reflecting said image to the eye of a viewer;
and
means for moving said reflecting means from a first position to a
second position.
10. An eye protection device comprising:
a liquid crystal light valve for providing an image of a scene;
means for supporting the light valve to facilitate the viewing
thereof;
reflector means for reflecting said image to the eye of a viewer;
and
folding mirror means for folding the optical train of said
device.
11. The invention of claim 10 including relay lens disposed in the
optical train of said light valve.
12. An eye protection device comprising:
a liquid crystal light valve for providing an image of a scene;
means for supporting the light valve to facilitate the viewing
thereof, and
means for inverting the image provided by said light valve.
13. The invention of claim 12 including twisting fiber mounted in
the optical train of said light valve.
14. An eye protection device comprising:
a liquid crystal light valve for providing an image of a scene;
and
means for supporting the light valve to facilitate the viewing
thereof, wherein said means for supporting the light valve includes
counter weights mounted on a helmet on which said device is
installed.
15. Eye protection goggles comprising:
two reflective liquid crystal light valves for providing an image
of a scene;
an objective lens for, one for each light valve, mounted along the
optical train thereof;
an eyepiece lens, one for each light valve, mounted along the
optical axis thereof; and
means for supporting the light valves to facilitate the viewing
thereof.
16. The invention of claim 15 including light emitting diode means
for reading said light valves.
17. The invention of claim 15 including reflector means for
reflecting said image to the eye of a viewer.
18. The invention of claim 17 including means for moving said
reflecting means from a first position to a second position.
19. The invention of claim 17 including folding mirror means for
folding the optical train of said device.
20. The invention of claim 19 including relay lens disposed in the
optical train of said light valves.
21. The invention of claim 15 including means for inverting the
image provided by said light valves.
22. The invention of claim 21 including twisting fiber mounted in
the optical train of said light valves.
23. The invention of claim 15 wherein said means for supporting the
light valves includes counter weights mounted on a helmet on which
said device is installed.
24. A target locator system comprising:
liquid crystal light valve goggles for imaging a scene in a
spectral range suitable for human viewing, wherein said liquid
crystal light valve includes a photoconductive layer, and
a head-up display.
25. An eye protection device comprising:
at least one liquid crystal light valve goggle for imaging a scene;
and
a helmet to which said at least one liquid crystal light valve
goggle is pivotally attached,
said liquid crystal light valve goggle including:
a photoconductive layer for receiving input images;
means on said photoconductive layer for blocking threat radiation,
and
a layer comprising liquid crystal for modulating a readout light
and replicating the input images for viewing in response to the
input images received by said photoconductive layer.
26. The eye protection device of claim 25 further including:
a light emitting diode mounted for optical illumination of the
viewing surface of said light valve.
27. The eye protection device of claim 25 wherein said liquid
crystal light valve further includes heating electrodes.
28. The eye protection device of claim 25 wherein said goggle
further includes a polarizing beam splitter having a holographic
lens fabricated thereon.
29. The eye protection device of claim 25 wherein said means for
blocking threat radiation includes:
metal matrix mirror having pixels and channels between said pixels,
and
a reflective layer covering both said pixels and said channels.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to eye protection devices. More
specifically, the present invention relates to techniques for
preventing eye damage due to high intensity laser radiation.
While the present invention is described herein with reference to
illustrative embodiments for particular applications, it should be
understood that the invention is not limited thereto. Those having
ordinary skill in the art and access to the teachings provided
herein will recognize additional modifications, applications, and
embodiments within the scope thereof and additional fields in which
the present invention would be of significant utility.
2. Description of the Related Art
The threat of the use of laser radiation to induce vision
impairment has prompted a concern for the ocular welfare of
personnel operating in hostile environments. This has lead to the
recognition of certain requirements to insure adequate eye
protection against such threats. Generally, the eye protection gear
should have a broad spectrum to block incident radiation over a
wide bandwidth. The eye protection device should have a zero
response time to insure that the device will react quickly enough
to protect the eye from short pulses of intense radiation. It
should operate independent the angle and polarization of the
incident radiation. It should be sensitive to energy in the visible
to near infrared range. The device should have a fast recovery time
and a high damage threshold.
Conventional eye protection technologies do not adequately meet
these requirements. Multi-channel image intensifiers can be used as
efficient image converters for eye protection. These devices
utilize photosensitive materials which generate electrons. The
electrons are amplified and bombarded on a phosphorous screen to
create an image of a scene.
Unfortunately, the photo-cathode of image converters are typically
susceptible to breakdown in response to an intense laser pulse. The
recovery time from such breakdown is too slow for many current
applications. And these devices tend to be complicated often
requiring high voltages. This class of devices also includes
electrochromic effect based goggles which tend to be too slow and
have a extinction coefficient which is too low (viz., energy
leakage too high) for the noted application.
Visors based on narrow band filters implemented with multiple
optical thin film layers can only reject radiation at known
wavelengths. No protection is provided against arbitrary radiation
in the broad visible spectrum such as that resulting from a dye
laser.
Nonlinear optical materials in the desired region remain as an
unproven concept. No optical material is known which features
sufficiently high sensitivity and response time to meet the
demanding requirements of eye protection. In addition, the leakage
of any such devices would probably be too high.
Thus, there is a need in the art for a broad spectrum, zero
response time angle and polarization independent, sensitive eye
protection device having a fast recovery time, high extinction
coefficient and a high damage threshold.
SUMMARY OF THE INVENTION
The need in the art is addressed by the eye protection device of
the present invention which comprises a liquid crystal light valve
for providing an image of a scene. The light valve images the field
of view under observation in a spectral range which matches the
human eye. It will automatically reject a laser threat by simply
absorbing the energy therefrom in the photoconductive layer
thereof. Thus, the invention provides a broad spectrum, zero
response time, angle and polarization independent, sensitive eye
protection device having a fast recovery time, high extinction
coefficient and a high damage threshold. Hence, the invention is
expected to be of significant utility to personnel operating in
hostile environments.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of the eye protection goggles of the present
invention mounted on a helmet of conventional design.
FIG. 2 is a perspective view, partially in section, of an
illustrative implementation of the liquid crystal light valve
(LCLV) of the present invention.
(FIG. 3 is a sectional side view of a single goggle of the
illustrative implementation of FIG. 2.
FIG. 4 is a schematic diagram of a silicon liquid crystal light
valve.
FIG. 5 is a first alternative embodiment of the eye protection
device of the present invention.
FIG. 6 is a second alternative embodiment of the eye protection
device of the present invention.
FIG. 7 is a third alternative embodiment of the eye protection
device of the present invention.
DESCRIPTION OF THE INVENTION
Illustrative embodiments and exemplary applications will now be
described with reference to the accompanying drawings to disclose
the advantageous teachings of the present invention.
FIG. 1 is a side view of the eye protection goggles 10 of the
present invention mounted on a helmet 12 of conventional design.
The goggles 10 are pivotally attached to the helmet 12 by a
modified Anvis bracket 14. Counter weights 16 mounted on the rear
of the helmet 12 counteract the weight of the goggles 10 on the
front of the helmet 12. As shown in phantom in FIG. 1, the goggles
10 include an objective lens 18, a twisting optical fiber 19, a
silicon liquid crystal light valve (LCLV) 20, and an eyepiece lens
22. The distance 24 represents the eye relief between the eyepiece
lens 22 and the eye 26 of the observer 30.
FIG. 2 is a perspective view, partially in section, of an
illustrative implementation of the liquid crystal light valve 10 of
the present invention. The left and right goggles 32 and 34 are
encased within a frame 35 constructed of plastic or other suitable
material. The embodiment of FIG. 2 shows first and second straps 36
and 38 for retaining the goggles 32 and 34 in a proper viewing
position. A green LED 54 is used as a readout light source.
FIG. 3 is a sectional side view of a single goggle of the
illustrative implementation of FIG. 2. As shown more clearly in
FIG. 3, each goggle 32 and 34 includes the objective lens 18, the
liquid crystal light valve 20, a polarizing beam splitter 40 and
the eye piece lens 24.
As illustrated in FIG. 4, the light valve 20 is of a conventional
reflective design including a silicon photoconductive layer 42, a
dielectric mirror 44, a first conductive electrode layer 46 of
indium-tin-oxide (ITO) or other suitable material, a liquid crystal
layer 50, a second ITO layer 48, and a glass layer 52. The design
and construction of liquid crystal light valve 20 is known in the
art, see for example "The Silicon Liquid-Crystal Light Valve", by
U. Efron et al., in Journal of Applied Physics. vol. 57, no. 4, pp.
1356-1368, Feb. 15, 1985.
A single crystalline silicon LCLV was chosen for the following
reasons:
1) the spectral range of the silicon photoconductor is extensive
(0.4-1.12 .mu.m);
2) the response time of the LCLV (typically 20 msec) is adequately
fast for the human eye (approx. 100 msec.) response;
3) the resolution of the device at an aperture of 3-4 cm may exceed
1000 lines, which is the estimated required resolution for the
human eye;
4) the room-temperature operation of the device is, of course,
compatible with the temperature of the human body; and
5) the sensitivity of the Si-LCLV is equivalent to a dimly lit
room, allowing operational range between full daylight and possibly
a moonlit scene, (further sensitivity can be achieved by
incorporating gain into the device using the avalanche principle,
for example).
The use of a silicon photoconductor also allows imaging in the near
infrared region (up to approx. 1.1 .mu.m due to the large thickness
of the silicon wafer. In order to block infrared and near infrared
threats, a metal matrix mirror can be constructed using metal grid
lines or the method of overhanging channel protection. In both
methods, the pixels as well as the channel areas around the pixels
will be covered by a reflective metal (e.g. aluminum) and will
therefore block any infrared threat from reaching the eyes. For
imaging mid-1R radiation, some leadsalts photoconductors, such as
PbS, PbSe, PbTe and their alloys can be used.
In operation, the objective lens 18 focuses the input image onto
the liquid crystal light valve 20. The photoconductive surface 42
of the light valve 20 receives the input energy and generates
electron hole pairs which are driven by an applied electric field
to cause a voltage drop on the liquid crystal layer. These
spatially resolved voltages induce a phase change of the readout
light thereby replicating the input image on the viewing side of
the light valve 20. The silicon photoconductor 42 allows imaging in
the 400-700 nm spectral region used by the human eye and will
automatically absorb any excessive high intensity radiation. If,
however, the input light intensity is outside the dynamic range of
the light valve, i.e., one to several hundred microwatts per square
centimeter, the output image will be slightly blurred. The degree
of image blurring is proportional to the incident light intensity.
As the incident laser pulse exceeds approx. 10.sup.7 W/cm.sup.2, a
local damage on the silicon will appear. The readout light
intensity (approx. 100.mu.W/cm.sup.2) is controlled by the current
of the LED used which can be powered by a 9-volt battery or by a
solar cell. Thus, a high intensity beam of a potentially blinding
level of say >50 watts/cm.sup.2, could be reduced by over five
orders of magnitude to a safe brightness level incident on the
observer's eyes. The LCLV goggles can also be incorporated with a
head-up display to serve as a threat locator, range finder or
target designator.
Returning to FIG. 2, a light emitting diode (LED) 54 is mounted
within the frame 35 of the device 10 between the left and right
goggles 32 and 34. As illustrated in FIGS. 3 and 4, light from the
LED may be injected onto the viewing surface of the light valve at
the glass 52 by the polarizing beam splitter 40 to facilitate
readout. In order to cut down on power consumption, ambient light
may be utilized during daytime by opening windows (e.g. at the
upper part of the goggles) to replace the LED operation. The LED
would be used when the ambient light is at a low level.
FIG. 4 shows a color filter 56 for making a color display from the
use of white light illumination. The color filters are deposited on
each pixel in the photoconductor and dielectric mirror sides.
In order to allow operation of the LCLV under cold weather
conditions, heating electrodes (not shown) could be used combined
with proper thermal insulation of the LCLV structures. If
adequately insulated from the surroundings, it may be possible to
rely on body temperature to supply the necessary heat for
maintaining the temperature of the LCLV.
In order to reduce the length of the goggles, a holographic lens
may be fabricated on the output window of the beam splitter 40.
The twisting optical fibers 19 (shown in phantom in FIG. 1) serve
to invert the image on the light valve for an upright presentation
to the viewer. FIG. 5 shows an alternative technique for
reorienting the image. In this embodiment 10', the LCLV 20 is
situated between two folding mirrors 60 and 62. The output image is
directed through the eyepiece lens 22 to a mirrored glass prism 64.
The prism 64 inverts the image and passes it to the eye 26 via a
folding mirror 66 and a holographic reflector 68 inside the lens of
the goggle 35.
The second alternative embodiment of FIG. 6 shows the use of an arm
70 constructed of reflective acrylic relay material. The arm 70 is
movable into and out of the line of sight of the eye 26. The arm 70
includes two aluminized reflective surfaces 72 and 74. Optical ray
traces are shown for the purpose of illustration.
FIG. 7 is a third alternative embodiment 10"' of the eye protection
device of the present invention. In this embodiment, a relay lens
80 is situated between two of four folding mirrors 60, 62, 64 and
66 to bend the optical axis downward or upward thereby shortening
the length of the goggles while simultaneously inverting the
image.
Thus, the present invention has been described herein with
reference to a particular embodiment for a particular application.
Those having ordinary skill in the art and access to the present
teachings will recognize additional modifications applications and
embodiments within the scope thereof. For example, the invention is
not limited to the optical arrangements illustrated herein.
It is therefore intended by the appended claims to cover any and
all such applications, modifications and embodiments within the
scope of the present invention.
* * * * *